Ok. The 2013 Euro Mazda 5 has the same transmission as a Volvo V50 - which is actually manufactured by Ford.
Here are some photos of the very easy replacement of the backup switch for a 2013 European version Mazda 5 1.6L diesel with a 6 speed manual transmission. Find the backup switch from the top of the motor, underneath the air intake box. The air intake is very easy to remove.
Here is the location of the backup switch, under the air intake box (air intake removed):
Here is a close up of the switch location on top of the transmission. Disconnect the quick connect electrical fitting, remove the old switch with an adjustable wrench, and reinstall the new one.
Here is the new switch, the old switch, and the box - clearly labeled Ford.
Hope this helps someone else.
For Vasy - yes, for such a new car, I would think it would be under warranty as well, but it was not. At 45,000 miles, I have needed one new fuel injector, a slave cylinder, and now a backup switch. I'm not happy about the quality of the Mazda parts so far.